Electronically tunable quad-band antennas for handset applications

ABSTRACT

An electronically tunable quad-band antenna which includes a tunable high band antenna tuned by at least one tunable varactor associated therewith; the tunable high band antenna further includes a substrate, a patch element on said substrate, at least one voltage tunable varactor associated with the patch element, a DC bias point on the patch element, an RF input on the patch element, and a temperature sensor associated with the high band pass antenna. Also included in a preferred embodiment of the electronically tunable quad-band antenna of the present invention is a tunable low band antenna tuned by at least one tunable varactor associated therewith, the tunable low band antenna further including a substrate, a patch element on said substrate, at least one voltage tunable varactor associated with said patch element, a DC bias point on said patch element, an RF input on said patch element, and a temperature sensor associated with said low band pass antenna. Also included is a controller receiving control data, and receiving output information from said low band antenna and output information from said high band antenna and controlling a first bias voltage for biasing the at least one voltage tunable varactor associated with the high band antenna and a second bias voltage for biasing the at least one voltage tunable varactor associated with the low band antenna. The bias voltages can be provided by a DC to DC converter regulator.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 60/445,348, “ELECTRONICALLY TUNABLE QUAD-BAND ANTENNAS FORHANDSET APPLICATIONS” filed Feb. 05, 2003, by Khosro Shamsaifar.

BACKGROUND OF THE INVENTION

The present invention relates generally antennas and more specificallyto tunable antennas and still more specifically to tunable quad-bandantennas for handset applications.

The current trend in mobile communications is in providing more andbetter services to the subscribers. Modern multi-mode, multi-band mobilephones will give better coverage and provide more data rates. This putsvery stringent requirements on the components of the transceivers,including the antennas, which must handle these new features.

A Quad-Band handset radio transceiver is an example of a multi-mode,multi-band system. It covers the following frequency bands andstandards:

-   824-894 MHz;-   880-960 MHz;-   1710-1880 MHz;-   1850-1990 MHz;-   GSM850;-   EGSM;-   GSM 1800; and-   PCS 1900.

In order to provide for quad-band antennas the need exists to provide agood match to the transmit and receive modules over more than 15% oftheir frequency bands. This may not always be achievable withoututilizing sophisticated and expensive antennas. Using expensive andsophisticated antennas with consumer handsets is problematic. Therefore,a strong need in the industry exists for quad-band antennas withexcellent performance and is cost effective.

SUMMARY OF THE INVENTION

The present invention provides an electronically tunable quad-bandantenna which includes a tunable high band antenna tuned by at least onetunable varactor associated therewith; the tunable high band antennafurther includes a substrate, a patch element on the substrate, at leastone voltage tunable varactor associated with the patch element, a DCbias point on the patch element, an RF input on the patch element, and atemperature sensor associated with the high band pass antenna. Alsoincluded in a preferred embodiment of the electronically tunablequad-band antenna of the present invention is a tunable low band antennatuned by at least one tunable varactor associated therewith, the tunablelow band antenna further including a substrate, a patch element on thesubstrate, at least one voltage tunable varactor associated with thepatch element, a DC bias point on the patch element, an RF input on thepatch element, and a temperature sensor associated with the low bandpass antenna.

Also included in a preferred embodiment of the electronically tunablequad-band antenna of the present invention is a controller receivingcontrol data, and receiving output information from the low band antennaand output information from the high band antenna and controlling afirst bias voltage for biasing the at least one voltage tunable varactorassociated with the high band antenna and a second bias voltage forbiasing the at least one voltage tunable varactor associated with thelow band antenna. The first and second bias voltages can be provided bya DC to DC converter regulator. In one preferred embodiment of thepresent invention the quad band antenna covers the following frequencybands and standards: 824-894 MHz; 880-960 MHz; 1710-1880 MHz; 1850-1990Hz; GSM850; EGSM; GSM 1800; and PCS 1900.

The present invention also provides for a method of transmitting andreceiving RF signals from multiple frequency bands utilizing anelectronically tunable multiple band antenna, comprising the steps of:providing a high band antenna with at least one voltage tunable varactorassociated therewith, the high band antenna providing a first input to acontroller; providing a low band antenna with at least one voltagetunable varactor associated therewith, the low band antenna providing asecond input to the controller; and inputting control data to thecontroller and controlling a first bias voltage for biasing the at leastone voltage tunable varactor associated with the high band antenna and asecond bias voltage for biasing the at least one voltage tunablevaractor associated with the low band antenna.

The controller of the present method can use a DC voltage supply toprovide the DC voltage needed to bias the voltage tunable varactors. Thehigh band antenna of the present method can further comprise: asubstrate; a patch element on the substrate; at least one voltagetunable varactor associated with the patch element; a DC bias point onthe patch element; an RF input on the patch element; a temperaturesensor; and a ground plane on one side of the substrate.

The low band antenna of the present method can further comprise: asubstrate; a patch element on the substrate; at least one voltagetunable varactor associated with the patch element; a DC bias point onthe patch element; an RF input on the patch element; a temperaturesensor; and a ground plane on one side of the substrate.

In a more specific embodiment of a preferred method of the presentinvention the multiple band antenna is a quad band antenna and coversthe following frequency bands and standards: 824-894 MHz; 880-960 MHz;1710-1880 MHz; 1850-1990 Hz; GSM850; EGSM; GSM1800; and PCS 1900.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top and side perspective of a preferred antennaconfiguration of the present invention with Parascan Tunable Capacitorsincorporated therein;

FIG. 2 illustrates the layout of the quad-band tunable patch antennas(TPA) system with controller of a preferred embodiment of the presentinvention;

FIG. 3 is a block diagram of the quad-band tunable patch antennas (TPA)system with the controller of a preferred embodiment of the presentinvention;

FIG. 4 is a graph depicting the return loss of a fixed antenna; and

FIG. 5 is a graph depicting the return loss of a tunable antenna at twotuning stages.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides electronically tunable antennas used inmulti-band, multi-mode mobile phones applications. The preferred tuningelements are voltage-controlled tunable dielectric capacitors placed onthe antenna package. The present technology makes tunable antennas verypromising in the contemporary mobile communication system applications.Thus, it is an object of the present invention to provide a tunableantenna for Handset applications, which, in a preferred embodimentconsists of two tunable antennas in the same package. The first antennacovers the low band (824-960 MHz), and the second antenna covers thehigh band (1710-1990 MHz). Both of the antennas need to provide a goodmatch to the transmit and receive modules over more than 15% of theirfrequency bands. In typical architectures, this would not always beachievable without going to sophisticated and expensive antennas.However, this problem can easily be solved by using an electronicallytunable antenna. With a tunable antenna, a good match can always beobtained at the frequency of interest. Inherent in every tunable antennais the ability to rapidly tune the response using high-impedance controllines. The assignee of the present invention has developed and patentedtunable materials technology such as the tunable filter using tunabledielectric capacitors set forth in U.S. Pat. No. 6,525,630 entitled,“Microstrip tunable filters tuned by dielectric varactors”, issued Feb.25, 2003 by Zhu et al. This patent is incorporated in by reference.Also, patent application Ser. No. 09/457,943, entitled, “ELECTRICALLYTUNABLE FILTERS WITH DIELECTRIC VARACTORS” filed Dec. 9, 1999, by LouiseC. Sengupta et al. This application is incorporated in by reference.

The assignee of the present invention and in the patent and patentapplication incorporated by reference has developed the materialstechnology that enables these tuning properties, as well as, high Qvalues resulting low losses and extremely high IP3 characteristics, evenat high frequencies. The articulation of the novel tunable materialtechnology is elaborated on in the patent and patent applicationincorporated in by reference.

Electronically tunable dielectric capacitors or varactors are used astuning elements. The varactors are mounted on the antenna block and arebiased using a DC bias circuit. By changing the bias voltage of thevaractors, their capacitance will change, which will tune the frequencyresponse of the antenna. There is also a temperature sensor on theantenna that reads the current temperature at any time and inputs theinformation to the controller. The controller will provide the correctvoltage at any temperature to tune the antenna to the desired frequency,using a look up table. The data in the look up table are generatedpreviously through a calibration process.

Turning now to the figures, FIG. 1 shows a top and side perspective of apreferred antenna configuration of the present invention with ParascanTunable Capacitors incorporated therein, wherein FIG. 1 at 102 shows thetop view of a tunable patch antenna 100 utilized in a preferredembodiment of the present invention. Included in tunable patch antenna100 is substrate 125 on which a patch element 110 is placed. Atemperature sensor 105 is also associated with substrate 125. On patchelement 110 is placed a DC bias point 115 and RF input 120. The DC biaspoint 115 provides bias to Parascan® Varactors (i.e., voltage tunabledielectric varactors) 130.

Shown at 150 is the side view of patch antenna 100, with DC Bias point115 and RF input 120 shown from the side perspective. Ground 155 is moreeasily seen in the side perspective 150 as is the thickness, shown at160.

FIG. 2, shown generally as 200, illustrates the layout of the quad-bandtunable patch antennas (TPA) system with controller of a preferredembodiment of the present invention. The Bias Circuits are not shown butare well known to one skilled in the art. High band antenna 205 isplaced within antenna package 250. Low band antenna 210 is also placedwithin antenna package 250. The output 215 of low band antenna 210 andthe output 220 of high band antenna 205 is input to controller 240.Control data 225 is also input to controller 240. Bias voltage 230 and245 are also provided to bias voltage controlled varactors (shown withreference numerals in FIG. 1) associated with high band antenna 205 andlow band antenna 210.

FIG. 3, shown generally as 300, is a block diagram of the quad-bandtunable patch antennas (TPA) system with controller of a preferredembodiment of the present invention. Microprocessor 325 receives inputfrom temperature sensor 315 and temperature sensor 360 as well ascontrol data 320. Temperature sensor 315 senses temperature informationfrom TPA low band 310, and temperature sensor 360 senses temperatureinformation from TPA high band 355. This temperature information andcontrol data is used, via a look up table, to determine the correctoutput for DC to DC to Converter/Regulator 330, thereby providing forthe correct bias voltage. Vdc is provided to DC to DCConverter/Regulator 330 at 335. DC to DC Converter/Regulator 330 outputsbias voltage 345 to the tunable varactors (not shown in FIG. 3)associated with TPA low band 305 and bias voltage to the tunablevaractors (not shown in FIG. 3) associated with TPA high band at 355. RFport 305 is provided for TPA low band and RF port 350 is provided forTPA high band.

FIG. 4 at 400 is a graph of Frequency 410 vs. Return Loss 425 depictingthe return loss of a fixed antenna and thereby the performance of thecurrent fixed antenna solution. The useable band 405 is the intersectionof line 430 at the −6 dB level 415 and the vertical intersection of theline formed by the intersection of the line at the −10 dB return losslevel. This shows that at higher frequencies it gets degraded (it showsonly −6 dB of return loss at the upper edge of the band), because of thebandwidth limitation of the antenna.

The instantaneous bandwidth of the antenna is smaller, which can resultin a better match. By providing tunability, at any frequency ofoperation within the useable bandwidth, the good match can be providedeverywhere.

FIG. 5, shown generally at 500, is a graph depicting the Return Loss 535vs. Frequency 505 of a tunable antenna at two tuning stages. The firsttuning stage is low tuning at 525 and the second tuning stage is thehigh tuning at 530. These are the two extremes. The usable band 510 isthe intersection of return loss at −10 dB. As it can be seen from FIG. 5the antenna will always provide a good match over the entire frequencyband of interest.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample, and not limitation. It will be apparent to persons skilled inthe relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed. Any such alternate boundaries are thus within the scope andspirit of the claimed invention. Thus, the breadth and scope of thepresent invention should not be limited by any of the above-describedexemplary embodiments, but should be defined only in accordance with thefollowing claims and their equivalents.

All cited patent documents and publications in the above description areincorporated herein by reference.

1. An electronically tunable multiple band antenna, comprising: a highband antenna with at least one tunable element associated therewith,said high band antenna providing a first input to a controller; a lowband antenna with at least one tunable element associated therewith,said low band antenna providing a second input to said controller; andsaid controller further receiving control data and controlling a firstbias for biasing said at least one tunable element associated with saidhigh band antenna and a second bias for biasing said at least onetunable element associated with said low band antenna.
 2. Theelectronically tunable multiple band antenna of claim 1, furthercomprising a DC voltage supply provided to said controller.
 3. Theelectronically tunable multiple band antenna of claim 1, wherein saidhigh band antenna further comprises: a substrate; a patch element onsaid substrate; at least one voltage tunable varactor associated withsaid patch element; a DC bias point on said patch element; and an RFinput on said patch element.
 4. The electronically tunable multiple bandantenna of claim 3, wherein said high band antenna further comprises atemperature sensor associated with said high band pass antenna.
 5. Theelectronically tunable multiple band antenna of claim 3, wherein saidhigh band antenna further comprises a ground plane on one side of saidsubstrate.
 6. The electronically tunable multiple band antenna of claim1, wherein said low band antenna further comprises: a substrate; a patchelement on said substrate; at least one voltage tunable varactorassociated with said patch element; a DC bias point on said patchelement; and an RF input on said patch element.
 7. The electronicallytunable multiple band antenna of claim 3, wherein said low band antennafurther comprises a temperature sensor associated with said low bandpass antenna.
 8. The electronically tunable multiple band antenna ofclaim 3, wherein said low band antenna further comprises a ground planeon one side of said substrate.
 9. The electronically tunable multipleband antenna of claim 1, wherein said multiple band antenna is a quadband antenna.
 10. The electronically tunable multiple band antenna ofclaim 9, wherein said control data is information to enable tuning forreception and transmission of predetermined frequency bands.
 11. Theelectronically tunable multiple band antenna of claim 10, wherein saidquad band antenna covers the following frequency bands and standards:824-894 MHz; 880-960 MHz; 1710-1880 MHz; 1850-1990 Hz; GSM850; EGSM;GSM1800; and PCS
 1900. 12. A method of transmitting and receiving RFsignals from multiple frequency bands utilizing an electronicallytunable multiple band antenna, comprising the steps of: providing a highband antenna with at least one voltage tunable varactor associatedtherewith, said high band antenna providing a first input to acontroller; providing a low band antenna with at least one voltagetunable varactor associated therewith, said low band antenna providing asecond input to said controller; and inputting control data to saidcontroller and controlling a first bias voltage for biasing said atleast one voltage tunable varactor associated with said high bandantenna and a second bias voltage for biasing said at least one voltagetunable varactor associated with said low band antenna.
 13. The methodof transmitting and receiving RF signals from multiple frequency bandsutilizing an electronically tunable multiple band antenna of claim 12,further comprising providing a DC voltage supply to said controller. 14.The method of transmitting and receiving RF signals from multiplefrequency bands utilizing an electronically tunable multiple bandantenna of claim 12, wherein said high band antenna further comprises: asubstrate; a patch element on said substrate; at least one voltagetunable varactor associated with said patch element; a DC bias point onsaid patch element; and an RF input on said patch element.
 15. Themethod of transmitting and receiving RF signals from multiple frequencybands utilizing an electronically tunable multiple band antenna of claim12 wherein said high band antenna further comprises a temperature sensorassociated with said high band pass antenna.
 16. The method oftransmitting and receiving RF signals from multiple frequency bandsutilizing an electronically tunable multiple band antenna of claim 12,wherein said high band antenna further comprises a ground plane on oneside of said substrate.
 17. The method of transmitting and receiving RFsignals from multiple frequency bands utilizing an electronicallytunable multiple band antenna of claim 12, wherein said low band antennafurther comprises: a substrate; a patch element on said substrate; atleast one voltage tunable varactor associated with said patch element; aDC bias point on said patch element; and an RF input on said patchelement.
 18. The method of transmitting and receiving RF signals frommultiple frequency bands utilizing an electronically tunable multipleband antenna of claim 12, wherein said low band antenna furthercomprises a temperature sensor associated with said low band passantenna.
 19. The method of transmitting and receiving RF signals frommultiple frequency bands utilizing an electronically tunable multipleband antenna of claim 12, wherein said low band antenna furthercomprises a ground plane on one side of said substrate.
 20. The methodof transmitting and receiving RF signals from multiple frequency bandsutilizing an electronically tunable multiple band antenna of claim 12,wherein said multiple band antenna is a quad band antenna.
 21. Themethod of transmitting and receiving RF signals from multiple frequencybands utilizing an electronically tunable multiple band antenna of claim20, wherein said quad band antenna covers the following frequency bandsand standards: 824-894 MHz; 880-960 MHz; 1710-1880 MHz; 1850-1990 Hz;GSM850; EGSM; GSM1800; and PCS
 1900. 22. An electronically tunablequad-band antenna, comprising: a tunable high band antenna tuned by atleast one tunable varactor associated therewith; said tunable high bandantenna further comprising: a substrate; a patch element on saidsubstrate; at least one voltage tunable varactor associated with saidpatch element; a DC bias point on said patch element; an RF input onsaid patch element; and a temperature sensor associated with said highband pass antenna; a tunable low band antenna tuned by at least onetunable varactor associated therewith said tunable low band antennafurther comprising: a substrate; a patch element on said substrate; atleast one voltage tunable varactor associated with said patch element; aDC bias point on said patch element; an RF input on said patch element;and a temperature sensor associated with said low band pass antenna; acontroller receiving control data, output information from said low bandantenna and output information from said high band antenna andcontrolling a first bias voltage for biasing said at least one voltagetunable varactor associated with said high band antenna and a secondbias voltage for biasing said at least one voltage tunable varactorassociated with said low band antenna.
 23. The electronically tunablequad-band antenna of claim 22, wherein said first and second biasvoltages are provided by a DC to DC converter regulator.
 24. Theelectronically tunable quad-band antenna of claim 22, wherein said quadband antenna covers the following frequency bands and standards: 824-894MHz; 880-960 MHz; 1710-1880 MHz; 1850-1990 Hz; GSM850; EGSM; GSM1800;and PCS 1900.